摘要:

SummaryPasteurella multocidatransconjugants isolated after mating withEscherichia colistrains that carry one or the other of two Tn7‐containing suicide plasmids, pRKTV5 and pUW964 (pRKTV5::Tn5), were analysed. These plasmids have the C0IEI replication origin and were thus expected to deliver transposons but not be maintained as free replicons inPasteurella.Five out of six transconjugants selected for acquisition of Tn7 fromE. coli(pRKTV5) had simple insertions of the transposon, in either orientation, at a single chromosomal location, while the sixth had pFtKTV5 integrated at the same location. By contrast, all of 27 transconjugants selected for acquisition of either Tn7 or Tn5 fromE. coli(pUW964) maintained pUW964. Of seven subsequently examined at the molecular level, all had pUW964 (in one case, a deletion derivative) integrated at the same location as the Tn 7 insertions obtained with pRKTV5. A copy of Tn7 was present at each boundary between the integrated plasmids (pRKTV5 or pUW964) and the chromosome in each strain. The two copies of Tn7 at either end of an integrated plasmid were either in the same (six cases) or in opposite (two cases) orientations with respect to each other. These seem to be products of replicative transposition by Tn7but can also derive from conservative mechanism

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1990.tb02019.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

SummaryThe G + C content of silent sites in codons varies greatly amongSerratia marcescensgenes; the value in any one gene seems to reflect a balance between mutation pressure towards high G + C content and natural selection constraining choice among synonymous codons. Interestingly, non‐coding sequences have substantially lower G + C content than silent sites thought to be under little selective constrain

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1990.tb02020.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

SummaryThe gene encoding thec.105 kD secreted haemolysin protein of the porcine pathogenActinobacillus pleuropneumoniaeserotype 1 has been isolated by screening a lambda gt11 expression library inEscherichia coliwith antiserum raised against the wild‐type protein. A derivative recombinant DNA pJFF702 expressed thehlylAhaemolysin gene from the pUC19lacpromoter but the resulting haemolysin I protein remained within theE. colicell and was haemolytically inactive. Export of the intracellularA. pleuropneumoniaeprohaemolysin out into the medium was achieved by the presencein transof theE. colihaemolysin secretion geneshlyBandhlyD, and high levels of intracellular haemotytic activity were attained similarly by theE. colipost‐translational haemolysin activator gene,hlyC.Southern hybridization ofA. pleuropneumoniaeparental DNA nevertheless indicated only a low degree of nucleotide sequence identity to the haemolysin structural and secretion geneshlyAandhlyBofE. coli.The data show that despite substantial nucleotide sequence divergence theA. pleuropneumoniaeserotype 1 haemolysin determinant is closely related to that which is dispersed throughout other Gram‐negative human and animal path

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1990.tb02021.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

SummaryExpression of the 7E and 2C genes late inDictyosteliumdevelopment ceases upon cell disaggregation but, in contrast to many other genes we have studied, expression is fully restored by exogenous cAMP (A. J. Richardset af., submitted). The 7E and 2C genes encode polypeptides of similar size (9220 and 10573 Daltons, respectively), each of which contains an unusually high proportion of serine plus glycine residues (41% and 59%, respectively). Each protein possesses a relatively serine‐rich N‐terminus and glycine‐rich C‐terminus and contains the conserved sequence S(X)SSS(X2)SS(X)SS(X2)SFGS. These data suggest that genes 7E and 2C may have arisen by duplication of a common ancestor. Computer analysis indicates that both gene products are probably intra‐cellular structural proteins that form extended coil s

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1990.tb02022.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

SummaryIn spite of displaying the most extreme dormancy and resistance properties known among living systems, bacterial endospores retain an alert environment‐sensing mechanism that can respond within seconds to the presence of specific germinants. This germination response is triggered in the absence of both germinant and germinant‐stimulated metabolism. Genes coding for components of the sensing mechanism in spores ofBacillus subtilishave been cloned and sequenced. However, the molecular mechanism whereby these receptors interact with germinants to initiate the germination response is unknown. Recent evidence has suggested that in spores ofBacillus megateriumKM, proteolytic activation of an autolytic enzyme constitutes part of the germination trigger react

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1990.tb02023.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

SummarySignal peptides play an essential role in protein trans‐location. This review summarizes the current knowledge of the structure of signal peptides and signal peptide‐lipid interactions and addresses the possibility that signal peptide‐lipid interactions initiate membrane translocation of precursor proteins. A new model for protein translocation inEscherichia coliis proposed, which includes as central features con‐formational changes of the signal peptide and signal‐peptide‐induced local changes in membrane organization (non‐bi

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1990.tb02024.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

SummaryUntil recently, tetracycline efflux was thought to be the only mechanism of tetracycline resistance. As studies of tetracycline resistance have shifted to bacteria outside the Enterobacteriaceae, two other mechanisms of resistance have been discovered. The first is ribosomal protection, a type of resistance which is found in mycoplasmas, Gram‐positive and Gram‐negative bacteria and may be the most common type of tetracycline resistance in nature. The second is tetracycline modification, which has been found only in two strains of an obligate anaerobe (Bacteroides).Recent studies have also turned up such anomalies as a tetracycline efflux pump which does not confer resistance to tetracycline and a gene near the replication origin of a tetracycline‐sensitiveBacillusstrain which confers resistance when it is ampl

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1990.tb02025.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

ISSN:0950-382X    

DOI:10.1111/j.1365-2958.1990.tb02026.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY